Although the predisposing causes of dreams may be sought for in more than one direction, they are probably in general referable to some peculiar condition of the body, and are often called into action through the agency of the external senses. Dr. Gregory relates, that having occasion to apply a bottle of hot water to his feet at bed-time, he dreamed that he was walking up Mt. Etna, and found the ground insufferably hot. Dr. Reid having had a blister applied to his head, dreamed that he was scalped by a party of Indians. M. Gizon de Buzereinges made a series of prearranged experiments, with the view of seeing how far he could determine at pleasure the character of his dreams. In his first experiment, having allowed the back of his head to be uncovered during sleep, he thought that he was at a religious ceremony in the open air; the custom of the country in which he lived being to keep the head covered, except or{ some rare occur relic-es, among which was the performance of religious ceremonies. On waking, he felt cold at the back of the neck, as he frequently had felt when present at the real ceremo nies. He repeated the exepriment in two days with the same result. In a third experi• meut, he left his knees uncovered, and dreamed that he was traveling at night in the diligence; and all travelers know, he observes, that it is chiefly at the knees that they feel cold when traveling by that conveyance at night.
One of the most remarkable phenomena of D., is the rapidity with which long trains of thought pass through the mind. A dream requiring hours for its accomplishment, is begun and terminated in a few seconds. A person who was suddenly aroused from sleep by a few drops of water sprinkled in his face, dreamed of the events of an entire life in which happiness and sorrow were mingled, and which finally terminated with an altercation upon the borders of an extensive lake, in which his exasperated companion, after a considerable struggle, succeeded in plunging him. Dr. Abercrombie relates a similar case of a gentleman, who dreamed that he had enlisted as a soldier, joined his regiment, deserted, was apprehended, carried back, tried, condemned to be shot, and at last led out for execution. After all the usual preparations, a gun was fired; he awoke with the report, and found that a noise in an adjoining room had both produced the dream and aroused him from sleep. Dr. Carpenter mentions the case of a clergyman falling asleep in his pulpit during the singing of the psalm before the sermon, and awakening with the conviction that he must have slept for at least an hour, and that the congregation must have been waiting for him; but on referring to his psalm-book, he was consoled by finding that his slumber had lasted not longer than during the singing of a single line. Sir Benjamin Brodie, in his Psychological Inquiries (1854), mentions the following anecdote of the late lord Holland: " On an occasion when he was much fatigued, while listening to a friend who was reading aloud, he fell asleep and had a dream, the particulars of which it would have occupied him a quarter of an hour or longer to express in writing. After he woke, he found that he remembered the begin
nino. of one sentence, while he actually heard the latter part of the sentence immedi atelY following it, so that probably the whole time during which he had slept, did not occupy more than a few seconds." Many facts of .the same kind are on record, and as the author from whom we have quoted, remarks, "if were to pursue this subject, it would lead us to some curious speculations as to our estimate of time, and the difference between the real and the apparent duration of life." It is from cases of this nature that lord Brougham has been led to the opinion, that all our dreams really take place in the act of falling asleep or of awaking. We cannot, however, explicitly accept this doctrine. 1. There is no sufficient proof of its being true. 2. We have a proof to the contrary in the fact, that it is common for people to moan and even talk in the middle of a sleep; and every one who has kept a dog must frequently have observed him dreaming (from the outward manifestations which he makes in the form of snarling or growling), though he still remains asleep. Some, on the other hand, have argued that the mind can never be entirely inactive, and that every one is dreaming throughout the whole period of sleep, although the dreams may not be remembered in the waking state. We know of no facts that can be adduced in favor of this hypothesis, and the following case goes strongly to disprove it: A woman, aged 26, who had lost a portion of the scalp, skull, and dura Mater, so that a portion of her brain was exposed to view, was a patient in 1821 in the hospital at Montpellier. When she was in a dreamless state, or in profound sleep, her brain was comparatively motionless, and lay completely within its bony case; but when the sleep was imperfect, and the mind was agitated by dreams, her brain moved and protruded from the skull, forming what is termed cerebral hernia. This protrusion was greatest when the dreams, as she reported, were most vivid; and when she was perfectly awake, especially if actively engaged in conversation, it attained its highest development, nor did this protrusion occur in jerks, alternating with recessions, as if caused by arterial action, but remained permanent while the conversation continued. If the data of this case are to be depended on, the appearance of the brain during profound sleep seems to indicate that during that state there is a total or nearly total suspension of the mental faculties.